Stephen Hawking wants you to meet the neighbours - they're a bit odd

THEY aren't just any aliens - they are extraterrestrial life as only one of the universe's best brains could envisage them.

Stephen Hawking has taken advantage of the latest computer graphics to display his versions of alien life forms, based on hard science, for a new documentary series, Into the Universe.

The British theoretical physicist, trapped in a body paralysed by motor neurone disease, and author of the best seller A Brief History of Time, spent three years to finish the series, which airs this weekend on the Discovery Channel.

The 68-year-old suggests in the first episode that extraterrestrials are almost certain to exist.

He points out the universe has 100 billion galaxies, each with hundreds of millions of stars and that in such a huge place, Earth is unlikely to be the only planet where life has evolved.

"To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually be like," he said.

The famous physicist has said it could be "too risky" to make contact with any extraterrestrial life, MSNBC reports.

"We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet," Prof Hawking said.

"I imagine they might exist in massive ships ... having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach."

"In truth, banning broadcasts would be impractical - and manifestly too late. We have been inadvertently betraying our presence for 60 years with our television, radio and radar transmissions," Dr Shostak said.

"The earliest episodes of I Love Lucy have washed over 6000 or so star systems, and are reaching new audiences at the rate of one solar system a day. If there are sentient beings out there, the signals will reach them."

Dr Shostak, a member of the Search for Extraterrestrial Intelligence (SETI), said only a society close to our level of development could pick up any intential broadcast and a society at our level is no threat.

Here is a taste of Hawking's aliens:

1. Gas giants

Planets like Jupiter and Saturn are a common type. But what would survive in such dense and violent atmospheres? If blimp-like creatures such as these roamed the hydrogen-helium atmospheres, one possible source of life-sustaining energy could come from harvesting lightning’s electrical discharges. But the combination of this atmosphere and the lack of a temperate solid surface would make the genesis of life as we understand it a real challenge

2. A sucker for E.T.

On an imaginary Earth-like world, lizard-like predators with limb membranes that allow them to glide use venom-loaded stingers to bring down a two-legged herbivore that has a huge vacuum snout to suck up food. Aliens on such a terrestrial planet would probably feed and move in ways similar to those here on Earth

3. Under the sea

A squid-like creature feeds on the bottom of the salty ocean thought to exist below the icy crust of Jupiter’s moon Europa. The moon is the only large body, other than Earth, that may have large volumes of water capable of supporting life. If organisms exist in this perpetually dark sea, they may exhibit characteristics of Earth’s deep-sea creatures, including the glow of bioluminescence and a nutrient chain based around hydrothermal vents

4. Abominable aliens

Life on planets where the average temperatures are down to the levels of liquid nitrogen (colder than -150C) would require organic components and physiologies radically different than those found on terrestrial planets largely dependent on liquid water. In this imagining, a multi-legged beast with thick fur to ward off the intense cold makes heavy going in the powerful winds that would be a constant on this demanding planet

Into the Universe with Stephen Hawking is on the Discovery Channel on Sunday at 7.30pm

News.com.au's Privacy Policy includes important information about our collection, use and disclosure of your personal information (including to provide you with targeted content and advertising based on your online activities). It explains that if you do not provide us with information we have requested from you, we may not be able to provide you with the goods and services you require. It also explains how you can access or seek correction of your personal information, how you can complain about a breach of the Australian Privacy Principles and how we will deal with a complaint of that nature.